The ATSB has released the investigation into a fatal Angel Flight crash in Victoria in August 2011.
The aircraft was on a flight from Essendon to Nhill in the state's west went it crashed in deteriorating weather near Wallup. The pilot and one passenger died at the scene and the third person on the plane died later in hospital.
According to the report, the accident happened because "the pilot probably encountered reduced visibility conditions approaching Nhill due to low cloud, rain and diminishing daylight, leading to disorientation, loss of control and impact with terrain."
At Essendon, the pilot had apparently been worried about the weather and planned to fly north before taking up a track for Nhill. The pilot landed at Bendigo unplanned and checked the weather again before continuing.
"Two witnesses, who were located about 2 km south of the accident site, reported observing the aircraft circle their position before descending and disappearing from view behind trees as it flew to the north," the report states.
"Moments later they heard a loud bang that they associated with the aircraft impacting the ground. The witnesses indicated that there was light rain at the time and that the aircraft’s engine sounded ‘normal’ before the accident."
Other pilots flying in the area reported conditions that were not suitable for VFR flight, including one who had been forced to do a low-level circuit on arrival at Horsham only minutes before the crash and another who reported the cloud base in the area at 500-800 feet.
GPS data recovered from a tablet computer on board showed the aircraft did a lot of turns and deviations just prior to the crash.
The full investigation report can be downloaded from the ATSB website.